Field of the Invention
The invention pertains to apparatus and methods for analyzing periodic movements in machinery. More particularly, the invention pertains to a non-contacting system for analyzing vibrations and other periodic movements in machinery and process equipment for predictive maintenance and other purposes.
Description of Related Art
All machines and moving systems produce vibrations of various kinds, some of which may be characteristic of normal operation and others of which may indicate off-normal conditions, unusual wear, incipient failure, or other problems. In the field of predictive maintenance, the detection of vibrational signatures is a key element of the diagnostic process in which the goal is to identify and remedy incipient problems before a more serious event such as breakdown, failure, or service interruption occurs.
U.S. Pat. No. 8,515,711 to Mitchell et al. proposes that wireless telemetry systems, including point sensors mounted directly on a turbine component, may provide more accurate measurement of component temperature and vibrations. The disclosed system may comprise a diagnostic system that combines the high fidelity data obtained by the point sensors with the broad area data associated with the same components and obtained simultaneously by surface measurement techniques. Calibration of the surface measurement techniques via point sensors located in the field of view on the same components may result in high fidelity data being obtained from a large surface area of the turbine components.
U.S. Pat. No. 9,006,617 to Mullen describes a monitoring system for monitoring the temperature and vibration of equipment, comprising a central digital computer, a MESH communication network, a plurality of heating elements for heating the equipment, and temperature/vibration sensors adapted to measure the temperature of the equipment. The central computer uses the data it receives from the other elements of the monitoring system to determine when the equipment is not at the correct temperature/vibration and diagnoses the reason why.
U.S. Pat. No. 8,924,163 to Hudson et al. discloses a vibration data collection and rotating machinery fault diagnostic instrument that includes a machine setup engine, a measurement engine, a diagnostic engine, a measurement user interface module, a machine setup user interface module, and a diagnostic user interface module. The means of acquiring vibration data are disclosed to be either single-axis or tri-axial accelerometers.
It has long been known that one can analyze the current in a motor to probe various conditions of the motor and equipment that is driven by the motor, using various signature analysis techniques. U.S. Pat. No. 6,774,601 to Swartz et al. discloses a system and method for predicting mechanical failures in machinery driven by induction motors by using the motor as a diagnostic tool to detect present mechanical disturbances. The motor is monitored during operation to avoid down-time. The motor's torque fluctuations are used as an indicator of early-stage mechanical failures in the machinery. The motor's torque fluctuations are determined using indirect sensing techniques that are less expensive and less intrusive than previously known. More specifically, torque is derived from easily and inexpensively measurable parameters, such as motor slip and phase angle. Current operation is compared to known normal operation. Variations of the motor's characteristics from the known baseline indicate an actual or approaching mechanical failure. “Experimental Fractals” are disclosed that visually represent a current state of the monitored machinery and allow for visual comparison to a baseline for detection of mechanical failures. Future failures are forecast by extrapolating a derived trend. U.S. Pat. No. 6,727,725 to Devaney et al. discloses a method to detect motor bearing damage using wavelet analysis of the motor current transient during startup.
Each of the foregoing methods relies on having physical contact with the machine system, either in the form of mechanical accelerometers affixed to the machinery, or by an electrical diagnostic connection in the power line. Each method also requires a specific physical solution for a specific component
Many industrial processes involve moving components or workpieces that may vibrate in characteristic (and possibly diagnostic) patterns, but are not amenable to physical contact. Examples include: a moving paper web, either in raw papermaking or in printing operations, moving sheet metal in rolling, heat treating, and finishing operations; moving items on a conveyor; rolling components such as individual rollers that support an elevated conveyor, moving extruded products, such as metal wire, polymer tubes, and the like. It will be appreciated that in each of these situations, important process control and/or predictive maintenance information may be found.
For all of the foregoing reasons, what is needed is a general, non-contacting method for analyzing general vibration processes, particularly in a factory or production environment, that does not need to be custom-built or installed on one particular piece of equipment and may be conveniently deployed on an ad hoc basis to create and maintain a database of historical vibration data for any selected number of individual equipment components or process points.